Thermal management for electronics using nonconductive magnetic particles

Abstract

Compositions for thermal interface materials comprising magnetically-alignable, thermally-conductive, electrically-nonconductive particles in a matrix comprising curable polymers are provided. The compositions are also useful for use as heat sinks. Methods are provided for the use of such compounds for thermal management and heat dissipation in the electronics industry.

What is claimed is: 
     
         1 . A composition for use as a thermal interface material or a heat sink in electronic circuitry, said composition comprising a plurality of thermally-conductive, electrically-nonconductive, magnetically-alignable particles suspended in a matrix comprising an electrically-nonconductive curable polymer, wherein the thermal conductivity of the particles is greater than that of the matrix, wherein in the presence of an applied magnetic field, the particles in the uncured composition align to form thermally-conductive, electrically-nonconductive structures along the magnetic field lines which structures are retained in the cured composition. 
     
     
         2 . The composition of  claim 1  wherein the particles comprise one or more of nickel, iron, cobalt, ferromagnetic rare earth elements, combinations or ferromagnetic alloys of any of the foregoing, hematite, ferrite, or magnetite. 
     
     
         3 . The composition of  claim 2  wherein the particles comprise FeNi, FeCoNi, or ferromagnetic alloys of iron with carbon or chromium. 
     
     
         4 . The composition of  claim 1  wherein the particles comprise a ferromagnetic core coated with a non-conductive coating such that the particles are substantially electrically-non-conductive. 
     
     
         5 . The composition of  claim 4  wherein the particles have a resistivity equal to or greater than about 10 8  Ω·cm in the relevant temperature range. 
     
     
         6 . The composition of  claim 2  wherein the coating comprises an electrically nonconductive oxide, nitride, sulfide, plastic, polymer, glass, clay, ceramic, quartz, fused silica, diamond, hematite, or magnetite. 
     
     
         7 . The composition of  claim 6  wherein the coating comprises NiO, SiO 2 , or Si 3 N 4 . 
     
     
         8 . The composition of  claim 2  wherein the average nominal size of the particles ranges from about 10 microns to less than about 100 microns. 
     
     
         9 . The composition of  claim 2  wherein the particles have a morphology that is at least partially spheres, flakes, crystals, rods, dendrites, or urchins, or is amorphous. 
     
     
         10 . The composition of  claim 1  wherein the matrix comprises an adhesive comprising silicone, solvent-based polymer, or solvent-free polymer. 
     
     
         11 . The composition of  claim 1  further comprising one or more additional thermally-conductive, electrically-nonconductive fillers which increase the net heat dissipation of the composition under conditions of use. 
     
     
         12 . The composition of  claim 1  comprising at least about 10% by weight of the particles to about 80% by weight of the particles. 
     
     
         13 . A heat sink comprising about 30% to about 80% of thermally-conductive, electrically-nonconductive, magnetically-alignable particles suspended in a matrix comprising an electrically-nonconductive curable polymer, and 0.1% to about 40% (w/w) of one or more thermally conductive, electrically-nonconductive fillers. 
     
     
         14 . The heat sink of  claim 13  further comprising a plurality of thermally-conductive, electrically-nonconductive structures in a cured state, said structures formed in response to a magnetic field applied to the heat sink in an uncured state, wherein the structures comprise particles aligned along the magnetic field lines. 
     
     
         15 . The heat sink of  claim 14  wherein the structures form microfins at the upper surface of the heat sink, wherein the microfins increases the effective surface of the heat sink and thereby increase the heat dissipation of the heat sink. 
     
     
         16 . The heat sink of  claim 13  wherein the particles comprise a ferromagnetic core coated with a non-conductive coating such that the particles are substantially electrically-non-conductive. 
     
     
         17 . The heat sink of  claim 13  wherein the particles have a resistivity equal to or greater than about 10 8  Ω·cm in the relevant temperature range. 
     
     
         18 . The heat sink of  claim 13  wherein the fillers increase the net heat dissipation of the composition under conditions of use and comprise aluminum nitride, aluminum oxide, boron nitride, or beryllia, silica, or quartz. 
     
     
         19 . A method of managing thermal properties of at least one electrical component comprising:
 applying a thermal interface material between the electrical component and a heat sink, wherein the thermal interface material comprises a plurality of thermally-conductive, electrically-nonconductive, magnetically-alignable particles suspended in a matrix comprising an electrically-nonconductive curable polymer;   subjecting the material to a magnetic field thereby causing the particles to align and form thermally-conductive, electrically-nonconductive structures along the magnetic field lines;   initiating the curing of the material by applying heat, or UV light; and   curing the material to produce a thermal interface layer;   wherein the thermally conductive structures are retained in the cured composition, and   wherein the thermal conductivity of the particles is greater than that of the matrix.   
     
     
         20 . The method of  claim 20  wherein the thermal interface material is a liquid, a semisolid, a gel, a paste, or a film, and the applying step comprises dispensing, coating, spraying, stenciling, dipping, depositing, 3D-printing, or covering with a film.